SF Technotes

Tesla Solar v. Mercedes Solar

By
Michael Castelluccio

May 24, 2017

1 comments

German automaker Mercedes-Benz has decided to engage in a head-to-head contest with Tesla–not with its line of luxury sedans, but with its line of home batteries. Tesla, you might recall, is in the process of creating what it calls a Gigafactory outside Sparks, Nev., that by 2018 will be producing more lithium ion batteries in one year than were produced worldwide in 2013.

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You can order a Tesla Powerwall battery for your home solar system today, direct from Tesla, but now, in this year’s second quarter, residents of California will be the first in the United States to be able to choose an alternate home energy storage system from Mercedes.

Last week in Lehi, Utah (home of Vivint Solar), and Sunnyvale, Calif. (central office for Mercedes-Benz Energy), the two companies announced “an exclusive strategic collaboration to bring the Mercedes-Benz customizable home energy storage system to the United States.” Vivint will design, install, and service the solar energy systems for your home, and Mercedes will provide the storage batteries for the system.

This is the first collaboration for Vivint to add storage batteries to its offerings. The company has installed solar systems in more than 100,000 American homes. And Mercedes-Benz Energy has been selling its solar storage batteries in Europe and South Africa. The rollout in California for this new partnership will begin in the second quarter of this year and then expand to other states later.

GOING OFF-GRID

Storage cells for the energy flowing from rooftop solar panels are the missing element in many current home installations. Without home batteries, these customers generally send the kilowatts their system generates out into power lines on the street and are essentially selling their output to the area’s electric supplier. They get credit on their electric bills, but if there’s a power outage from a storm or grid problem, their supply shuts off automatically. Letting it to continue to flow would endanger the linemen who are trying to make repairs on the street.

With charged storage cells, you can just switch over when there are outages. And there’s another advantage to having your own battery system. If you live in an area where time-of-use (TOU) electrical rates prevail, what you pay for power changes depending on the time of day. Peak hours, usually late afternoon and evening, will cost you more. With solar and a battery system, you can switch to the stored, free wattage during those hours. And if you’re using power company resources as well, you can schedule when you use solar direct or solar stored to minimize your bills.

THE TWO BATTERIES

The differences between the two storage cells aren’t that significant. You’ll probably want to put them in your garage near the home breaker box and the inverter, which is likely near the breaker panel but on an outside wall. As its name suggests, the Tesla Powerwall mounts on the wall, while the Mercedes battery sits on the floor against the wall. In the image below, the Mercedes battery shown is actually a stack of three separate 2.5 kWh (kilowatt-hour) batteries. To combine multiple Tesla batteries, you would probably mount them side by side.

Photo: Vivint solar

The Mercedes battery system is made up of 2.5- kWh batteries that are modular and can be stacked to a maximum 20 kWh. Prices for the batteries range from $5,000 for a single to about $13,000 for a 20 kWh system fully installed.

Photo: Tesla.com

The Tesla Powerwall 2 batteries provide 13.5 kWh and are $5,500 each. They can be combined in a single system up to a maximum of 10 cells.

The price and power differences would seem to overwhelmingly favor Tesla at this point, but keep in mind that Mercedes has now partnered with a major installer of solar panels, and premarketing has indicated that those looking to put in a system have a strong interest in storage cells. Vivint is one of the three largest residential solar installers in the country. On the other hand, Tesla purchased SolarCity late last year, and that installer is bigger than Vivint. This clash of giants certainly looks formidable.

Like the Gigafactory, this competitive alignment of the two industrial giants on the same field could provide a seismic lurch forward in the development of alternate renewable energy for the home. Add in the reasonable likelihood that these batteries would probably also be used to recharge the electric and hybrid vehicles from the two automakers, and you have another renewables dimension outside the home. Any way you look at it, the contest between Tesla and Mercedes should prove interesting and consequential.

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Michael Castelluccio has been the Technology Editor for Strategic Finance for 23 years. His SF TECHNOTES blog is in its 20th year. You can contact Mike at mcastelluccio@imanet.org.